In January 1997, the United States Environmental Protection Agency presented to the Congress of the United States of America their first report on the “Drinking Water Infrastructure Needs Survey” which defined an investment need of $138.4 billion over the next 20 years. $77.2 billion was determined for the replacement and rehabilitation of potable water transmission lines in order to deliver the quality and quantity of water required by customers. The problems found in the water distribution systems include (1) tuberculation which blocks the pipe and reduces the hydraulic capacity which then requires higher operating pressures and also reduces fire protection, (2) depletion of biocide due to the presence of tuberculation, organic matter and the microorganisms associated therewith, and (3) leaks resulting from microbiological and/or galvanic corrosion and higher operating pressures.
Fire protection systems are usually an extension of existing water distribution systems. The deterioration of piping, sprinkler heads and the hydraulics (the ability of the system to deliver water to design specifications) in fire protection systems is most frequently attributed to the quality of the water being supplied from the water distribution source, including potable water distribution sources. Contributing to the water quality feed problem is the fact that most fire protection systems are supplied through a “dead end” pipe connection from the water main to the fire protection system. These “dead ends” are notorious for containing all of the problem microbiological organisms that lead to the deterioration of the fire protection system. This is due to the stagnant nature of the water in the “dead end” which even allows biocides to be depleted and organisms to grow. Then, when the fire protection system is tested periodically, the stagnant, microbiologically contaminated water from the “dead end” is fed into the fire protection system which then begins or adds to the deterioration process.
In recent years, lawsuits have been filed against municipalities for supplying water that contains metal-hungry, corrosion-inducing bacteria which damage sprinkler systems and cause leaks that, in turn, further damage other assets. Municipalities argue that the water produced by their treatment plants meets or exceeds the specifications required for potable water. However, it is well documented that the quality of the water leaving the water treatment plant is not the same as that being consumed by the user after being transported through miles and miles of deteriorated distribution systems. This has recently led the EPA to require that potable water suppliers sample water at the user's taps and measure for lead and copper content (“The Lead and Copper Rule”). If the lead and/or copper content is over the maximum allowable content, then the supplier must take the appropriate action to lower the content to achieve acceptable levels. This is usually accomplished by the addition of passivation chemicals at the water treatment plant. Additional quality requirements by the EPA for water taken from the consumers tap are expected to be forthcoming in the future.
This situation is further compounded in fire sprinkler systems. For example, during periodic testing or under fire conditions, stagnant water which has been depleted of biocide and is now full of microbiological organisms from the “dead end” pipes contaminates the entire fire sprinkler system. In early 1996, the National Fire Protection Association (NFPA) began receiving reports regarding a significant increase in the number of problems involving the prevalence of pinhole leaks in fire sprinkler systems nationwide. A survey of the members was conducted in April of that year to determine the full extent of the problem. Pinhole leaks with dark brown or rust colored slime were reported on the interior of the piping. The source of this deterioration is now termed “Microbiologically-Influenced (or Induced) Corrosion” (MIC).
The NFPA's Pamphlet No. 13 “Installation of Fire Sprinkler Systems” is now revised to include and recognize MIC as a severe problem in fire protection systems and requires that it must be dealt with to ensure proper, long term fire protection system performance.
When it is determined that MIC is present and the eventual deterioration is underway, few options exist to deal with the problem in fire protection systems. Once pinhole leaks or nodules of tuberculation (which will markedly reduce water flow and which, under “fire” flow conditions, can break loose and block the sprinkler heads) are present, the affected pipe should be replaced. Then, steps must be taken to ensure microbiological infestation does not reoccur when the system is put back into service.
If there are no pinhole leaks or indications of tuberculation nodules, then thoroughly flushing the system with water containing biocides may reduce the problem. It is very difficult, however, to fully flush all of the pipe in a typical sprinkler system and ensure the removal of all microorganisms. Organisms can even penetrate the pipe threads at the fittings and may not be reached by a biocide flush. Also, if the system does not include a backflow prevention device on the supply line from a potable water main, only biocides which have been certified to NSF (National Science Foundation) International's Standard 60 may be employed to eliminate the contamination potential of a potable water feed system. Once the system has been flushed and placed in a restored but stagnant condition, microorganisms that have gone into a dormant state in the presence of the biocide can revive and thrive when the biocides are depleted.
If there are nodules of tuberculation present, but the integrity of pipe walls is still good, then pipe cleaning should be considered. U.S. Pat. No. 5,885,364 describes a chemical cleaning process which utilizes a chemical cleaning solution to remove the nodules of tuberculation that adhere to the interior walls of the pipe. Chemical cleaning, alone, can not guarantee sterilization of the system.
Mechanical cleaning technologies generally cannot be used in fire protection systems because of the elevations involved, the different sizes of small diameter pipe and the innumerable joints, elbows, etc. It would be more economical to replace the entire system.
Installation, replacement, repair, flushing or chemical cleaning of a fire protection system without sterilization and aseptic maintenance of the system merely postpones the inevitable re-infection and ultimate corrosion of the system. The need for a practical and efficient process to sterilize new and in-use fire protection systems, whether chemically cleaned or not, is urgent. Sterilized systems must also be maintained in an aseptic condition to ensure long term performance.